Emerging Technologies: Bowel Cancer Screening
DNA Stool Test
In August 2014, the US Food and Drug Administration (FDA) approved Cologuard, the first stool-based bowel cancer screening test that detects the presence of red blood cells and DNA mutations that may indicate the presence of certain kinds of abnormal growths that may be cancers such as bowel cancer or precursors to cancer.
Using a stool sample, Cologuard detects hemoglobin, a protein molecule that is a component of blood. Cologuard also detects certain mutations associated with bowel cancer in the DNA of cells shed by advanced adenomas as stool moves through the large intestine and rectum. Patients with positive test results are advised to undergo a diagnostic colonoscopy.
According to the FDA, faecal blood testing is a well-established screening tool and the clinical data showed that the test detected more cancers than a commonly used faecal occult test.
The FDA's approval of Cologuard does not change current practice guidelines for bowel cancer screening. Stool DNA testing (also called faecal DNA testing) is not currently recommended as a method to screen for bowel cancer in the United States.
The safety and effectiveness of Cologuard was established in a clinical trial that screened 10,023 people. The trial compared the performance of Cologuard to the faecal immunochemical test (FIT), a commonly used non-invasive screening test that detects blood in the stool.
Cologuard accurately detected cancers and advanced adenomas more often than the FIT test.
Cologuard detected 92 percent of bowel cancers and 42 percent of advanced adenomas in the study population, while the FIT screening test detected 74 percent of cancers and 24 percent of advanced adenomas. Cologuard was less accurate than FIT at correctly identifying subjects negative for bowel cancer or advanced adenomas.
Cologuard correctly gave a negative screening result for 87 percent of the study subjects, while FIT provided accurate negative screening results for 95 percent of the study population.
Dr. Frank Sinicrope, a professor of medicine and oncology at the Mayo Clinic said there are still 'important issues that await further research'. Those would include determining how best to deal with false positive results and establishing how often patients should take the DNA test to maximise its screening potential.
Bowel Cancer Blood Test
In May 2014, Australian researchers presented at an international medical conference in Chicago, Digestive Diseases Week, that the ColoVantage Plasma blood test for bowel cancer could detect 65% of bowel cancer cases increasing to 73% for cancers that are stage II or higher.
Julien Wiggins, chief executive, Bowel Cancer Australia said the research was taking us a step closer to accessing another effective screening option for bowel cancer.
"Bowel cancer is preventable and the existing faecal immunochemical tests (FIT) continue to play a key role in both prevention and detection, detecting around 90% of stage I bowel cancers."
"Despite this, screening rates remain low for a variety of reasons and it's unlikely we will see significant increases in participation for some years. This is an ongoing concern as Australia has one of the highest rates of bowel cancer in the world."
"A blood test may be an option for some who would otherwise choose not to screen at all. A proven option that could see more Australians screening can only be a good thing," he said.
According to Professor Graeme Young from the Flinders Centre for Innovation in Cancer at Flinders University in Adelaide, the test could be a candidate for population screening in the future and its sensitivity for cancer justifies prospective evaluation in a large screening population.
"If this test becomes available in the future I think the message would need to be that the faecal immunochemical test (FIT) is the best place to start for people who are due for screening. Then the blood test would be for those people who can't or won't screen with a FIT," said Professor Young.
Dr Larry LaPointe, CEO of Clinical Genomics, the company who co-developed the test with the Commonwealth Scientific and Industrial Research Organisation (CSIRO), says the test could be available in Australia on a 'user pays' basis as soon as early spring 2014.
"These results show the test has the potential to underpin a cost-effective blood test that identifies those with a curable bowel cancer. This has the potential to save many lives by complementing existing screening programs," added Dr LaPointe.
The results were based on blood specimens collected at an Australian and Dutch hospital from more than 2,000 volunteers who were scheduled for colonoscopy or for bowel surgery.
The new blood test is the result of more than a decade of collaborative research carried out by Australian biotech company Clinical Genomics, the CSIRO and the Flinders Centre for Innovation in Cancer based in Adelaide.
In July 2014, the first commercially available blood test for bowel cancer rolled out in the Blue Mountains, New South Wales as a pilot trial of ColoVantage Plasma.